1) Field of the Invention
The present invention relates to a plural liquid pack type, heat-curable polyisocyanate-polyolpolyepoxy resin composition and a process for producing a shaped resinous article from same. More particularly, the present invention relates to a plural liquid pack type, heat-curable polyisocyanate-polyol-polyepoxy resin composition having an excellent storage stability, handling property and molding property and useful for producing a shaped resinous article having a superior heat resistance, chemical resistance and mechanical strength, especially impact strength and machinability, and a process for producing a shaped resinous article therefrom at a high reproducibility and stability.
2) Description of the Related Art
Due to recent technological developments, various new types of resinous materials having an excellent heat resistance, mechanical properties, and moldability are now in demand.
Among these new resinous materials, the most noticeable is a reaction-molding type resin comprising a reactive monomer or oligomer. This reaction-molding type resinous material refers to a heat-curable resinous material having a relatively low viscosity, preferably being in the state of a liquid at room temperature, and capable of being simultaneously molded and cured (hardened or polymerized).
The heat curable resinous materials include polyurethane resins, and vinyl ester resins. Some of the above epoxy resins, and unsaturated polyester resinous materials which have been commercially produced and marketed.
Nevertheless, these conventional heat-curable resinous materials have some disadvantages. For example, the conventional polyurethane resins usually have a low heat resistance and the conventional unsaturated polyester resins and epoxy resins are too hard and fragile, although they have a higher heat resistance than that of the conventional polyurethane resins.
Japanese Examined Patent Publication No. 44-16669 discloses an improvement in the heat resistance of the conventional polyurethane resins, obtained by introducing an isocyanurate ring structure derived from a trimerization of an isocyanate compound thereinto. This improvement has long been known and practiced in the polyurethane resin industry, but is effective only for increasing a heat-distortion temperature of a heat-cured polyurethane resin by about 20.degree. C. to 30.degree. C., and thus the resultant heat-cured polyurethane resin exhibits a heat-distortion temperature of not higher than about 150.degree. C. to about 160.degree. C.
A well known heat-curable resin, produced by using, as a component, a polyisocyanate compound, is a heat curable resin having an oxazolidone ring structure derived from a reaction of an isocyanate group in a polyisocyanate compound with an epoxy group in an epoxy compound.
Japanese Unexamined Patent Publication No. 62-62879 disclosed a heat curable resin having the isocyanurate ring structure derived from a trimerization of an isocyanate compound together with the abovementioned oxazolidone ring structure.
This heat curable resin is advantageous in having an enhanced heat resistance, but is disadvantageous in having a high fragility and a poor-impact strength. This high fragility and poor impact strength are common disadvantages of the conventional heat-curable resins.
To eliminate these disadvantages, an addition of an elastic material, for example, a rubber material, to the conventional heat-curable resins has been attempted, but this addition of the elastic material does not effectively enhance the impact strength to a high degree. Also, an increase in the amount of the added elastic material causes the resultant product to exhibit a deterioration in properties other than the impact strength, for example, a lowered heat-distortion temperature.
The inventors of the present invention attempted to provide a liquid resinous composition comprising a polyisocyanate, a polyepoxy compound, a polyol compound and a curing agent. In this attempt, the inventors found that the resultant resinous composition is unstable due to a high reactivity thereof, and thus is easily cured or polymerized even at room temperature, and the viscosity of the resinous composition is increased and a gel-like or insoluble substance is formed. Accordingly, when a shaped resin article is produced from the resinous composition, the reproducibility of the properties of the shaped resin article is poor, and the molding procedure becomes unstable.
Japanese Unexamined Patent Publication No. 59-221321 discloses a process for producing a shaped resinous article from a resin composition. This resin composition comprises a first individual liquid resinous component comprising a liquid mixture of a polyisocyanate compound and an epoxy compound and a second individual liquid component comprising a liquid mixture of a specific curing agent, such as an aziridine compound with a tertiary amine compound, and optionally, an active hydrogen compound. In this process, the first and second individual liquid components are mixed, and the resultant mixture is then immediately subjected to a molding procedure, for example, a pour-molding or injection molding procedure.
The inventors of the present invention studied in detail the above-mentioned process and found that, in the first individual component, the polyisocyanate compound gradually reacts with the epoxy compound and a gel-like substance and an insoluble substance is formed in the first component with a lapse of time. When the epoxy compound has two or more epoxy groups, the above-mentioned phenomenon is significant, and thus the first individual component cannot be stably stored over a long time, and accordingly, cannot be practically utilized.